The use of waxes in cosmetic and dermatologic preparations is well known. Natural waxes in cosmetic formulation are solid or semi-solid mixtures of hydrocarbons, often used to confer or increase structure in a liquid matrix. They are also used to modify hardness, brittleness, flow and melt characteristics. Applied to the skin or hair, waxes create a water repellant film and therefore confer emolliency to those compositions in which a wax is deployed. Wax is not a chemically precise term. The substances to which the term is applied are, generally, malleable and hydrophobic and have a melting point above about 45° C. Chemically, waxes are lipids and may be esters of ethylene glycol (ethan-1,2-diol) and two fatty acids or they may be esters of a fatty acid with a fatty alcohol.
The most common cosmetic waxes are animal, mineral, vegetable or petroleum-derived. Synthetic waxes are also known and used in the cosmetics industry. Among animal derived waxes, beeswax is by far the most common and may act as a “reference” wax, while lanolin (wool wax) and spermaceti (from the sperm whale) have also been used in skin preparations. Okorite and ceresin are among the naturally occurring mineral waxes. Carnauba, candelilla and castor are well known cosmetic waxes of the vegetable type. Carnauba is the hardest natural wax and has the highest melting range (78-85° C.). Paraffins and microcrystalline waxes are among those derived from petroleum that also find use in the skin care field.
Structure vs. Payoff
The choice of which wax or blend of waxes to use depends, in part, on the amount of structure that must be imparted to the finished product. In turn, that amount of structure depends on the type of product and how the product is to be used and applied. A product with too much structure may not have good payoff or deposit on the surface being treated. That is it may take many applications to get a substantial amount of product onto the treated surface.
On the other hand, a product with too little structure, while having good payoff, is susceptible to smearing, either during or after application. It should also be understood that the majority of cosmetic and dermatologic products lose structure when sheared. Thus, when designing topical preparations it is necessary to consider the degree of shearing to which a product may be subjected up to the moment of application to the treated surface. A product that has a good amount of structure shortly after it is manufactured may lose structure by the time the product is applied by a consumer. The trick is to get to the consumer a product that still has an effective amount of structure, while providing good payoff.
When discussing shear, one has to understand thixotropy. Thixotropy refers to the property of some materials to exhibit a time-dependent change in structure (and viscosity) as a result of applied shear. By time dependent, it is meant that the longer the material undergoes shear, the greater the material's loss of structure and the lower its viscosity. Thus, in a product that is subject to shear by drawing across the skin, like lipstick, the product gets less viscous the longer it is used and that causes the payoff to be inconsistent. Thus, in getting to the consumer a product with an effective amount of structure and a consistent payoff, it is advantageous to develop products that have a time-independent response to shear, or as little time dependence as possible. From a structure point of view, products with lesser thixotropy are preferred.
Plasticizers
Products based on relatively hard waxes (high structure) confront the problem of poor payoff, by adding plasticizers to the formulation. In a conventionally executed formulation, the plasticizer softens the wax and improves payoff or deposit. Plasticizers, however, have drawbacks. For example, plasticizers may be irritating to the skin of a user. Also, plasticizers are chemically very different from the waxes on which they are intended to act. Therefore, conventional plasticizers introduce into the product, a foreign component having nothing to do with the real purpose of the product. What would be better is if the payoff of hard wax compositions could be improved by an additive that is much closer, chemically, to the base wax.
Flower Wax
Throughout the specification, “flower wax” refers to a substance obtained from any part of a flowering plant. For example, the wax may reside near the reproductive structure, on the leaves or on the fruit of the flowering plant. In practice, flower waxes are often obtained as a by-product of an essential oil extraction process. Some flower waxes useful in the present invention include, but are not limited to: apple, bitter orange, chamomile, jasmine, lavender, mimosa, narcissus, raspberry, rose and violet.
Flower waxes, as separate from the term “conventional waxes”, have found limited use in topical preparations. Flower waxes have not been used in stick products because conventional implementation leads to end products that lack sufficient structure immediately following manufacture, and made worse by subsequent shearing. For example, in lipstick, substitution of flower waxes for all of the conventional waxes renders the lipstick incapable of withstanding the necessary applied force. In use, the stick breaks or simply mashes when drawn (sheared) across the lips. Furthermore, flower waxes have not been used in stay-in-place products. By “stay-in-place” product we mean a product or portion thereof that remains atop the surface of the skin or hair, that does not evaporate or volatilize away, that is visible to the human eye and that generally requires mechanical force to remove. In cosmetics, many pigmented make-ups fit this definition. For example, stay-in-place product like mascara or foundation, made by substituting flower waxes for all of the conventional waxes, smudges too easily, during and after application.
On the other hand, compositions made with flower wax have relatively good deposit on skin and hair, in particular, brush-on mascara and hair products. Likewise, flower wax stick products (i.e. lipsticks and lip balms) have relatively good payoff onto the skin or lips. By “deposit” and “payoff,” we mean the amount of product transferred to a surface, regardless of the quality of the application. Also, flower waxes in general have a pleasant, fragrant component, while many waxes have no odor or even malodor. In any number of situations the fragrant component of flower wax would be considered a positive aspect of the material. Also, flower waxes are chemically more similar to conventional waxes than other additives, and the combination of flower waxes with conventional waxes is less likely to create compatibility problems. Thus it would be desirable to take advantage of one or more beneficial properties of flower wax, if the structure problem associated with flower wax could be mitigated. Unknown in the prior art is a method of rendering flower wax-based compositions less susceptible to shear.